Dietary plant derived lignans and isoflavonoids have been shown to have anti-estrogenic and estrogenic activity. Previous feeding studies have shown that consumption of foods with a high content of lignans and isoflavonoids resulted in elevated urinary excretion of these compounds and increased plasma concentrations of sex hormone binding globulin. Earlier studies have also indicated that breast cancer patients and women at high risk for breast cancer excrete lower amounts of lignans and isoflavonoids in their urine. Previous studies, however, have not investigated in detail the influence of plant lignans and isoflavonoids on hormonal status, physiological parameters and receptor tissue response to estrogen. In this study it is proposed to feed forty-two pre and postmenopausal women diets that have not been supplemented with a source high in flavonoids or lignans. Pre and post menopausal women have been selected, since there may be a differential response to phytocompounds based on existing endogenous estrogen levels. In premenopausal women midfollicular and luteal plasma and urine collections will be taken. The plasma collections will be analyzed for estrogens, androgenous and sex hormone binding globulin. The urine will be analyzed for isoflavonoids, lignans and estrogens. In addition, urine will be purified to remove estrogens and the purified faction will be studied to determine its effect on estradiol binding to uterine type I and II estrogen receptors and MCF7 breast tumor cell proliferation. Midfollicular plasma FSH and LH levels will be determined and length of menstrual cycle will be monitored. In postmenopausal women the same parameters will be measured in monthly urine and plasma collections and in additional vaginal epithelial cytology will be evaluated. These studies should provide data on the relative estrogenic to anti- estrogenic activity of plant lignans and isoflavonoids in pre and postmenopausal women. These data can provide information on the importance of specific plant foods in modifying exposure of target tissues to estrogen.